I've not been able to confirm if the slam fire parts will work in the newer guns, but I have a call in to the guys at Ithaca so I'll let you know what I find out.
We have a couple of the Defense Models listed on the site now:
https://www.aztecharmory.com/thaca-m...a-p-36974.html
https://www.aztecharmory.com/ithaca-...a-p-36973.html
https://www.aztecharmory.com/ithaca-...a-p-36972.html
We have access to their full catalog, so let us know exactly what you need and we will get it set up for you.